Delayed electromagnetic trip circuit breaker



Aug. 15, 1950 J, sANDlN ETAL DELAYED ELECTROMAGNETIC TRIP CIRCUIT BREAKER Filed May 17, 194'? 2 Sheets-Sheet 1 Aug. l5, 1950 J. sANDlN ErAL 2,519,291

DELAYED ELECTROMAGNETIC TRIP CIRCUIT BREAKER Filed May 17, 1947 2 sheets-sheet 2 /57 /57 f g 4. //Q g.

TTORN Patented Aug. 15, 1950 DELAYED ELECTROMAGNETIC TRIP CIRCUIT BREAKER -lerome Sandin, Forest Hills, and Herbert L. Rawlins, Edgewood, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 17, 1947, Serial No. 748,808

(Cl. 20D-109) 1l Claims.

This invention relates to circuit breakers and more particularly, to trip devices for controlling the automatic operation oi circuit breakers.

An object of the invention is to provide a circuit breaker embodying an improved trip device which is oi simple construction, reliable in operation and inexpensive to manufacture.

Another object oi this invention is to provide a circuit breaker with an improved electromagnetic trip device operable totrip the breaker after a relatively long time delay in response to overload currents of relatively low value, after a relatively short time delay in response to overload currents of intermediate value up to a predetermined value and instantaneously in response to overload currents above said predetermined value.

Another object of the invention is to provide a circuit breaker embodying an improved trip device wherein a time delay device disposed within a sealed casing functions to trip the breaker after a long time delay on certain overload current conditions and also after a relatively short time delay on certain other overload current conditions.

Another object of the invention is to provide a circuit breaker embodying an improved trip device having a time delay device disposed in a sealed casing which is movableto trip the breaker, the time delay device within said casing delaying tripping of the breaker for a relatively long time on low overload currents and delaying tripping of the breaker for a relatively short time on overloads oi intermediate value.

Another object of the invention is to provide a circuit breaker embodying an improved trip device (l) having sumcient time delay throughout the range of motor starting currents to permit the starting of motors having the highest values of locked rotor currents, approximately six to ten times normal rated current, (2) capable of providing the shortest permissible time delay necessary for selective tripping on current above locked rotor currents, (3) capable of tripping instantaneously in response to any fault current up to the short time delay rating of the breaker to provide maximum protection for equipment and other breakers when connected in cascade, (4) capable of wide range of pickup variation of the time delay element, (5) capable or operation on alternating current and direct-current breakers, (6) readily removable and interchangeable to facilitate changes in breaker ratings and tripping characteristics, and (7) that is reliable in.

operation over long periods and under all types oi service with a minimum oi maintenance.

The novel features that are considered characteristic of the invention are set forth in particular in the appended claims. The invention' itself, however, both as to structure and operation, together with additional objects and advantages thereof, will best be understood from theI Fig, 5 is a. View simiiar to rig. 4 but showing' the movable core structure in the position it assumes during a time delay tripping operation,

Fig. 6 is a view similar to Fig. 4 but showing the movable core structure in its instantaneous tripping position,

Fig. 7 illustrates variations in time-current curves obtained by the use of diiierent timing elements, and

Fig. 8 illustrates these time-current curves for these circuit breakers connected in cascade, the different time-current curves being obtained by the use of diiierent timing elements.

Referring to Fig. l of the drawings, the reference numeral ll designates a base of insulating material. A pair of terminals I3 and l5 are suitably secured to the base and are provided respectively with connecting studs ll and i9.

The contact means and mechanism of the circuit breaker illustrated are similar to the circuit breakers fully disclosed in Patent No. 2,214,471, issued September 10, 1940, to Leon R. Ludwig and Merle E. Horn, and assigned to the assignee of the instant invention. Hence, only a brief description of these parts will be given herein.

The stationary contact means comprises main stationary contacts 25-21 secured respectively to contact blocks 2l and 23, an intermediate contact 29 and a stationary arcing contact 3l.

The movable contact means comprises amain bridging contact member 55 having contactmembers ''l mounted thereon for cooperation withl the main stationary contacts 25-2l, a movable intermediate contact 6 which cooperates with the intermediate contact 29 and a movable arcing contact 'Il for cooperating with the stationary arcing contact 3|. The main bridging contact member 55, the movable intermediate contact 69 and the movable.rarcingfcontactgli areiall suitably mountcdion ccntecteearryina-.erm 49 whichY is; rigidly mounted on a pivoted switch member 5|.

The switch member 5| is operatively connected by means of a link 89 to an.aQtiuat-ng,` lever 85 pivotally mounted on a pivot' pin, 81;' supported in a main frame "19. The actuating lever 85 is release/bly connected-ato anoperatingr. member 9|, also pivoted on the` pin Si'lg bymeana of a pair of latches S3 and S5 which are pivotally mounted on the actuating lever` 35 at 9'! and 99- respectively. The latch 93 engages@ lathgollerg IUI carried by the operating member 9|, andis held in latching position by the latch 95- The operating member 9| is releasa'bly held in closed position.. by.. means. ofaV a main:v holding; latch. |932 pivotedf. at: |.-|.9,: which. releasably. engages. the.; latch-.roller I lIherlatch. 95:: is provided-L with. a. tailpiece. H351 by.l which. itl is operated to. .release .the ilatchf. gibl and'. consequent. tripping of the. circuit breakerY by. release. of.r the.. actuating. lever ilE. from the operating memberl; When releasedY the.- actuating lever.- 85.: is moved by means. of a. pain of accelerating-.springs iilS. (only one .beingshownl,

in a counterclockwise directionaboutits. pivoty 81, causing opening of the.. movable. contact means'.` During an.. opening movement. of, the actuating-A lever.v 85,-. a cani..Y surface |371 thereon engages the rounded nose of the main holding. latch. |lsand.movesv this latchrto effect release of.I theoperating. memberr ..l

In order to close the circuit breaker.- aftenit has beentrippedopen, the operatingrnemberel is rst movedicount'erclockwise to theropen-posip tiorrto reset the-latches and reestablish the connection between the operating.memberefll and the. actuatinglever 85. Thereafter, the operatingmember-isl moved clockwise.. toclosed position= by meansfoi-a .handled I to effect-:closing ofthe contact means.

The..circuit..-breaker isl arranged to .be trippedl open either manually, or to be trippedcautomatie, call-y in lresponse to. .predetermined overloads 1in the/.circuitgfby means.- of a..trip zmeansindicated generally at H5.

Theftrip device'comprisesa 'trip leverV I l'lpivotally; mounted intermediate its ends. on the.A frame'lS-byuneans of thepiyotpin-l I9; anelecf. tromagnetic trip; del/ieendicated generally at, |2l| ,L which ,isioperable in.A response.- to, predetermined.; overload currents.` to move the. .trinleverl Il to :tripping yposition toeiect automaticopem. ingoia-,the fcircuit-=breeker One.,'arrnv |23 of-thisgtripleyerf- Ill isolset and: extends. inwardly toward-thc basalt and h aeits inner endzdspcsed. above the, tripping.-V electioipagpet l2lto be engaged epdacperetedf byf ef. trip,pinfarl plunger to. effect automatic .tripi pingpfthe-,breaken The arml 23,012.; themtrip lever..- isl provided. with a.. projection.. i255. which.; upon:` piping operation of the.y trip arm.,y .engages theicurvedztalpiece .of thelatchfto move this-latch to tripping position.4` The other arrnvi ofthe trip-lever forms ahandle |2`|-swhereby the trip` lever may be manuallyancvedto, tripped position to. effect manual opening of the. circuit breaker. The, main latch Irisbiased to `latch-r ingzposition-,and the trip lever lllfis biased-to normal `position `by means.. oi, a'. spring |29cften.

4 sioned between the arm |23 of the trip lever and an extension of the holding latch.

The electromagnetic trip device |2| comprises generally a xed magnet yoke |3|, a movable core structure |33, a trip rod operable by the movable core structureandl an energizing winding-, |311 having one end;electrically. connected to the contact block 23 and the other end electrically connected to the terminal l5.

The Xed magnet yoke |3| is generally U- shaped and' is provided with mounting feet |39 by means of which the trip device is rigidly but removably mounted: on the base being secured theretobymeans of bolts Ml. The contact'- block 23 is electrically connected to the upper end of-the winding I3? by means of a short conductor- |43. The lower terminal stud I9 isformed at right angles and is rigidly secured tothe-front of the base l| by means of a bolt and nut |47 which also secures the terminal strip 15ste the studllS. Therwinding..-lf3lviisdnsulated-.fromfthe lower:leg.. of-= themagnetryoke 35|. and from the movable coretstructureby. means` ofv an insulating spool: 49.;

The movable.. core structure4 331 comprises a1 sealed? casing |51: of non-magnetic materialfofv stainless steel filled* with .a1 suitable.A fluid .silicone tolthel-level indicatedfby the dottediline inFig.- 2 andrhaving.. ancorey member or armature-1 |53. se-..

E cured-#to the lowenendithereof=byfany-suitable.-

means, for instance, byfbrazing, thus: sealingethe: lower end of the casing.; The upperV endrof.' the` casing Il` extends L through an opening inV the u-Dperleg of! the xedfmagnetr yokeI y| 3| andfhas 1a.: flange 551\` formedthereon .whichl normally. rests: on .the xed:` core-member-.- Al disc. .Y I :'s'lzsecured to the ange |55, as by welding, forms a closure for` theyA upper end' ofsthe'casingv 51.' which, togetheny withftheacoreimember |53; hermetically.

w seals .-thefcaSing:

Suitable iiuid;` polymeric;v organo-.siloxanes for: use-in.` the :sealedI casing` are polymeric: silicones.- havingr. the...following.1general formulan..

coneuids 0I ,various degrees.v ci viscosity at a given .temperature of; usef'may be.: employed.. the casing..v Itrispreferred tousea Yuid silicone of le :high viscosity, .for-.exampleone .-off: arvisccsity, of 1000 centistokes at ,-2 5-C. However, uidsofl aviscosity olfrcim,l aboutlglllto51(Lililflcentipoises-I at,25f. C. maybe :en iplo-yed.:vv

Someof .theadvantaeesgottbeefluid polymeric siliconesl are their smalLchange, in .viscosity with temperature. All,v the silicone. luidshave con. sderablyVv natter, viscosityftemicerature` curves: than petroleum llycirocarbprrs` or other organic. oils or liquids.. Thesilicone fluids may be used at. temperaturesA as low as 1i'. and temperatures of 'over 300"` They will `not gum or sludge under conditions-otuse. Theya-re characterizedl by outstanding stability.

Disposed With-in the sealed# casing |5| is Aan upper core` member.` or armature i lifhaving a conical i recess .or pole-'facce 62| in .theflower endlr thereof-for cooperatniglwiththe. pole/.face |63.

in the form of a truncated cone on the upper end of the core member |53. A bypass timing valve stem or valve housing |65 (Fig. 2) of nonmagnetic stainless steel disposed between the flat upper end of the pole face |63 of the core member l53 and the cover disc |51 extends axially through an opening in the upper core member |59, the diameter of the housing |65 being slightly smaller than the opening in the core member. A spring |51 surrounding the valve housing |65 and compressed between a shoulder on the upper core member |59 and the core members |53 biases the upper core member upwardly against a spacer 99 surrounding the upper end of the valve housing 555 above the upper core member |59.

, rEhe bypass valve housing |65 comprises :a hollow member closed at its upper end by an integral part of the housing and at its lower end by means oi a plug |1I, the inner end of which comprises a valve seat |13. The plug |1| is secured in the lower end of the housing |55 by any suitable means and is provided with an axially extending opening which cooperates with a transverse opening |11 in the lower end of the housing |65 to provide a passage which is normally closed by a bypass valve |19. The valve H9 is biased to closed position against the valve seat |13 by means of a coil spring |8| surrounding a valve stem |83 integral with the valve 19, the spring being compressed between the valve |19 and a shoulder |85 formed in the upper end of the valve housing. The valve stem 93 is guided in its opening and closing movements by a suitable guide opening |81 formed in the upper end of the housing. Ports |89 are provided in the side wall of the housing |65 at a point near the upper end thereof and the annual orii'lce between the housing |65 and the member |59 is larger above the ports |89 than it is below these ports to permit passage of fluid to the casing |5| above the upper core member l5@ upon .operation of the valve |19 as will be more fully described hereinafter.

The tubular lower end |9| of the core member is hollow and extends downwardly through an opening in the lower leg of the magnet yoke l9i and is surrounded by a tapered bushing |93 of magnetic material which is secured in the opening in the lower leg of the ilxed magnet yoke lei. The bushing |93 is counterbored to receive a bearing ring |95 of non-magnetic material for guiding the lower end of the movable core structure |33. rihe upper end of the movable core structure E33 is guided in its reciprocal movement by the casing |5| bearing directly against a reduced portion |91 of the upper leg of the iixed magnet yoke |3|.

Secured to the lower leg of the xed magnet yoke |3| is a U-shaped frame |99 held in place by a bracket 20| which is secured to the magnet yoke by means of screws (not shown). Disposed within the tubular lower end |9| of the core member |53 is an instantaneous trip armature 293 having bearing rings 205 of non-magnetic material secured thereto adjacent each end thereof. The armature 293 normally rests on an adjusting screw 291 threadedly engaging a bracket T299 supported between the sides of the frame i399. The adjusting screw may be turned in either direction to vary the position of the armature 293 relative to the core member |53 and is locked in its adjusted position by means of a lock nut 2| I.

Secured to the tubular extension |9| of `the core member |53 near the lower end thereof is a pair o1" spaced rings 2|3 having extensions 2|5 on one side thereof.y A generally U-shaped member 2 |1 has its legs pivotally mounted in V-shaped notches 2|9 (only one being shown) in the side members of the frame |99. The free end of the member 2|1 is biased by means of a spring 22| having one end anchored to the bight of the U-shaped member 2|1 and the other end attached to a U-shaped adjusting member 223. The member 223 is provided with laterally extending projections 225 which engage the front of a scale plate 221 secured to the frame |99 and is securely clamped in its adjusted position by means of an adjusting screw 229, the shank 23| of which extends through an opening in the member 223, a vertical slot 233 in the scale plate 221 and threadedly engages a rectangular nut 235 which spans the inside of the scale plate to adjustably clamp the member 223 to the scale plate.

The trip device functions within two ranges of overload currents below a predetermined value to trip the breaker after a relatively long time delay in the lower range of overload currents, and with a relatively short time delay in the intermediate range of overload currents, and also instantaneously in response to overload currents above the predetermined value, or in response to short circuits. The ranges of overload currents may be arbitrarily defined as follows: The low range up to 1090570 of normal rated current, between l0O0% and 2500% of rated current for the intermediate range, and 2.500% or more of rated current for the instantaneous tripping range. The limits of the intermediate range of overload currents set forth are to be considered merely by way of example and these may be varied considerably to suit particular requirements. For instance, by the provision of stronger or weaker springs entirely diierent sets of values may be established. The value of overload current at which the breaker will be instantaneously tripped may be varied by varying the position of the armature 293 or by varying the cross-sectional area or mass of the instantaneous tripping armature. Also, by replacing the bypass valve |19 and the valve housing |55 with a solid rod having the same outside diameter as the hou-sing, the short time delay on overload currents in the intermediate range may be eliminated in which case, only long time delay tripping and instantaneous tripping would be provided, and this time delay may be varied by providing rods of diierent diameter.

When a persistent overload occurs in the low range of overload currents, the magnetic circuit is energized but, due to the high density flux between the upper portion of the upper core member |59 and the reduced annular portion |91 of the fixed magnet yoke |3l, the core member |59 will iirst drop down slightly until the top of the member |59 is substantially in line with the lower face of the portion |91 and will then be held substantially in this position while the magnetic ux in the air gap I9 63 starts to move the core member |53 and the sealed casing |5| slowly upwardly. In the low range of overload currents, the upward pull on the core member |53 creates a pressure on the fluid in the casing |5| below the upper core member |59, but this pressure is insuflicient to overcome the spring |8| and open the bypass valve |19, consequently the uid is forced upwardly through the space between the valve housing |65 (Fig. 2) and the upper core member |59 thus providing a relatively long time delay before the sealed casing engages and operates the trip rod |351 to eiectf tripping the breaker. thel core memberk |53 and' thesealed casing- |-5| movev upwardl-ygthe air gapi-I-IBS-is gradually reduced thereby applyinga greater 'force to `-the sealed cas-- ihgatl the-time the casingengagesthe trip-mechanism-to eiect the-actual tripping of the-breaker.

some installations theshort time-delay tripping effected bythe bypass-.valve |79 may not be requiredin which event the bypass valve may'be omitted-and? al solidi timing stem |65? (Fig. 1-) of non-magnetiestainless steel substituted therefor. Intliis-'fcase7 the only orifice through which the iifuid may now from the space below the upper coreimember 1 iti 9 to the yspace kabove the-core member is the annular orifice between the rod |65 and the; member |59. Substitution of the solid rod i 551ifonthe bypass valve il@ provides inverse time-delayonoverload current valuesrup to 250% of rated current. This time delay may be Varied bytheprovision-of rods |65 of different diameter, thusivaryi'n'g the size of the annular orifice.

Beforev the sealed casingV can start its tripping movement; the-forces linthe lmagnetic circuit must be great enough to overcome theY weight of the several parts'and the" tension or the Calibrating spring 22 l. When this force is attained, the movable` core structure, through the projection 2|5 ori-theilowerring '2 i3, rotates the U-shapedmember ZIllV clock'wise'against the tension of the spring 221.v As: the upward; movement'of the movable core structure progresses, the movement oifl the member 2-"|"' reduces the moment arm with which the'force of the spring 2M is applied to the movable core structure, thereby-maintaining the ap'- plied restraining force of thespring 22| substantially'constant throughout the tripping movement of the movable core structure.

The minimum current'atwhich the'trip deviceV will functionY to trip the breaker may,V be varied by releasingthe adjusting screwY 29 and sliding the member '223 up ordown to the desired position as'indicated bysuitable indicia (not shown) on the scale plate 227; and then tightening the screw 229to lock the member 223 in the selected position. Movement of the member 223 in the slot 233 varies the tension. of thespring 22| and'also varies the moment arm at which the force of the spring is applied to the movable construction. By moving the member 223" upwardly far enough tocarry. the line of action of the spring1 22| over center above the member Ztl, the spring 22| will bias the core member 25.3 and the casing |5| in tripping direction thereby permitting lower minimum pickup settings.

`When the trip device is energized in response to' an overload currentv in the intermediate range ofl overload currents, the magnetic forces create a much greater pressure in the sealed casing |5| below the member |59. This pressure is'suicient toovercomethe force of the valve spring |8.| and open the valve Ils, thus permitting a greater rate of flow of the duid. past the member i 59'. By permitting an increased rate of Iiow of the fluid; the time delay is muchshorter in response to overloadcurrents within the intermediate range than itis on overload currents in the low range ofl values but appreciably longer than instantaneous tripping.

When the trip device is energized in response to an overload current above 2500% of rated current,v or a short circuit, the instantaneous trip armature'iiliy is actuated. This armature, when actuated, moves quickly upward striking a suitable impact absorbing material 231, such for example as -felt cir-leather, and: thereafter moving 8 th@ entire movable core lstructureJ |337lbodily upward; to= effectinstantaneous trippingoff the breaker.

After tlietrip device has functioned', either on' a time delay tripping operation' or on instantaneoustripping operation, theparts are returned to-their normal positions by gravity aidedby the Calibrating spring 212|; The spring |61 restores the upper coreelernent |59 upwardly to its normal position adjacent the stop (i9.-

Various combinations of elements may be assembledfinthel movable core structure toiproduce various tripping characteristics For instance; referringto Fig. 7, the instantaneous trip armature 2il3mayi bey omitted and the solid rod |65 assembledi'n the sealed casing. This wouldf result intime delay tripping with an inverse time delay onalll overload currents, as illustrated by curve iiiv (Fig. 7). Still omitting the instantaneous: tripVv armature and substituting thel bypass' device ITS# would result in relatively long time delay tripping on overload currents up to a predetermined value and tripping with a relatively short time delay4 on overload currents above the predetermined value, as shown by curve-C (Fig. 7)". Curve* BI (Fig: 6) shows the time-current curveobtained by using a solid timing stem of smaller diameter than is used to produce curveA, thus providing a short time delay for allva'lues' of fault currents. Again, by usingthe solid rod-|65 in combination with the instantaneousitrip armature 203; long time delay tripping would result on overloads up to a predetermined value and instantaneous tripping would be eected on overload currents above the predetermined value'shown at A--A', (Fig. 7). Also, as previouslydescribed, the instantaneous trip armature and the bypass valve device assembled in thetrip device results in theA combinationA of relatively long-time delay tripping on overloads inthe low range relatively short time delay tripping on overloads in the intermediate range, and instantaneous tripping on overload currents above-'aA predetermined value, or on short circuits.

The time characteristics for both long time delay and short time delay tripping may be changed by varying thesize of the annular'ori- :lice betweenv the rod` |65 or the valve housing |65 and the member |59; and by varying the size ofthe passage |15 (Fig. 2). B'y varying the strength ofthe valve spring I 8 I, the value of'overloadcurrent required to start the trippingoperation may bevariecl. Also the instantaneous trip characteristics may be varied by varying the mass and/or position of the instantaneous trip armature 203. Thusl thetripping characteristics may be varied over a wide range for each range of overload currents.

The variable characteristic obtained byy interchanging the several elements of the trip device, assetfforth above, well adaptsthe trip device for usein the selective tripping of circuit breakers; Fig. 8' illustrates the true current curves for a' typical' selectivity application. In this illustrative application a' 100 ampere load breaker is provided` with both long time delay and instantaneous tripping to permit motor starting as shown by curve C (Fig. 8). A 400 ampere feeder breaker equipped with-long time delay and short timedelay tripping curve B (Fig. 8) is providedl to-obtainselectivity with thefmotor startingf load? breaker. A 1600 ampere transformer breaker is providedl to supply power to the system. Thisbreaker is'equipped with short time de1ayf(-curveA, Fig. 8) only and is setto-pickeup at 3000 amperes. This provides for selectivity with the 400 ampere feeder breaker and all other feeder breakers. If the transformer is capable of delivering currents of greater magnitude than the interrupting capacity of the load and feeder breakers, both selective tripping and cascade tripping may be combined by providing the feeder and transformer breakers with instantaneous trip armature adjusted to trip on overloads equal to the interrupting capacity of the load and feeder breakers as indicated by the dotted portion D of the curves A and B (Fig. 8). In such an application selective tripping is obtained on overloads below the interrupting capacity of the load and feeder breakers and all breakers will trip instantaneously on overloads equal to the interrupting capacity of the load and feeder breaker.

I-Iaving described the invention in accordance with the patent statutes, it is to be understood that various changes and modifications may be made in the structural details and combination of elements disclosed without departing from some of the essential features of the invention.

We claim as our invention:

l. In a circuit breaker for controlling an electric circuit, the combination of an electromagnetic trip device comprising an energizing winding, a trip rod, a sealed casing movable to engage and actuate said trip rod, a rst armature having a portion disposed in said casing and a tubular portion outside of said casing, said armature being operable upon energization of said winding in response to overload currents to move said casing, means comprising a magnetizable core member having an axially disposed opening therethrough disposed in said casing and responsive to energization of said winding to oppose movement of said casing, and a member extending through said opening and movable with said casing for controlling the rate of tripping movement of said casing, and a second armature in said tubular portion operable to instantaneously move said casing to cause said casing to engage and instantaneously actuate said trio rod.

2. In a circuit breaker for controlling an electric circuit, the combination of an electromagnetic trip device comprising an energizing winding, a sealed casing containing a body of fluid and movable to eiect a tripping operation, a rst armature having a portion disposed in said casing and operable upon energization of said winding in response to certain circuit conditions to move said casing in tripping direction, means including an element having an axial opening therethrough disposed in said casing and held against movement in one direction by energization of said winding to provide a time delay in the tripping movement of said casing, a by-pass valve device in said opening movable with said casing for kcontrolling the rate of new of fluid through said opening to thereby control the rate of tripping movement of said casing, and a second armature disposed in axial alignment with said casing and operable in response to certain other circuit conditions to effect instantaneous tripping movement of said casing,

3. In a circuit breaker for controlling an electric circuit, the combination of an electromagnetic trip device comprising an energizing winding, a trip member, a sealed casing containing a body of iluid and movable to engage and actuate said trip member, a first armature disposed in -said casing and operable upon energizationof said winding in response to overload currents to move said casing, a second armature having a lil fluid passage disposed axially therethrough disposed in said casing and restrained against movement by energization of said winding, means biasing said second armature to one end of said casing, a valve housing disposed in said passage to be moved with said casing for restricting the flow of fluid past said second armature to control the rate of tripping movement of said casing in response to overload currents below a predetermined value, a by-pass valve in said valve housing for controlling the iiow of fluid to thereby control the rate of tripping movement of said casing in response to overload currents above said predetermined value, and a third armature disposed in axial alignment with said rst armature and operable to engage and move said rst armature and said casing to effect instantaneous operation of said trip member.

4. In a circuit breaker. the combination of an electromagnetic trip devi-ce comprising an energizing winding, a sealed casing containing a body of iluid and movable to effect a tripping operation, a first armature disposed in said casing and operable upon energization of said winding in response to overload currents below a predetermined value to move said casing, a tubular extension on said armature extending outside of said casing, a second armature having a fluid passage therethrough disposed in said casing to be restrained against movement by energization of said winding, a member disposed in said fluid passage and movable with said casing to control the flow of fluid through said passage to thereby control the rate of tripping movement of said casing, and a third armature disposed in said tubular extension and operable upon energizaticn of said winding in response to overload currents above said predetermined value to instantaneously move said casing.

5. In a circuit breaker, the combination of a trip device comprising an eectromagnet, a sealed ca-sing movable to eiect a tripping operation, an armature disposed in said casing operable upon energization of said electromagnet in response to overload ycurrents below a predetermined value to move said casing, a tubular extension on said armature extending outside of said casing, a magnetizable core member having a passage therethrough disposed in said casing to be held again-st movement in response to overload currents below said predetermined value, a member disposed in said passage to retard tripping movement of said casing, and an armature disposed in said tubular extension and operable in response to overload currents above said predetermined value to instantaneously move said casing to thereby effect an instantaneous tripping operation.

6. In a circuit breaker, the combination of a trip device comprising electromagnetic meansl forming a magnetic circuit, a sealed casing containing a body of uid and disposed for tripping movement within said circuit, a movable armature disposed in said casing to move within said magnetic circuit for -moving said casing, a magnetizable member disposed withinsaid casing to be held against movement by the magnetic flux in said magnetic circuit, said magnetizable member having an opening therethrough, a separate Valve housing disposed in said opening rigidly supported between said armature and one end' of said casing for movement with said casing relative to said ymagnetizable member, said valve housing cooperating with said magnetizable member to define a passage permitting a predetermined flow of iluid past said magnetizable member under s said.r winding,

certain conditions, valve meansin said housing operable under certainA other conditions to. increase the rate of flowA of. fluidpast. said magnetizable member, and a. second armature disposed-in axial alignment withsaid casing operable under certain other conditionsy to` instantaneously move saidcasing.

7.k In a circuit breaker, the combination of a trip. device4 comprising electromagnetic means forming a magnetic circuit, a sealed `casing of non-magnetizable material containing a body of fluid and` disposed for. tripping movement within saidy magnetic circuit, a rst armature disposed in. saidv casing to move rwithin. said. magnetic circuit for moving saidv casing, a magnetisable member having an opening therethrough and disposed. .within said casing to. be held against movement by the magneticV flux in said magnetic circuit, an element disposedl insaid opening rigidly supported betweensaid armature andY one end of said casing for movement with said casingv relative to said magnetizabe member, seid element cooperating with. said magnetizablemember to define an annular fluid passagepermitting displacement of fluid past said magnetizable member under certainv conditions, the rate of tripping movement of said casing being determined by the rate of displacement of fluid past said magnetizable member, and a second armature disposed below said casing operable under certain other conditionsto engage and instantaneously move said first armature and said casing,

8. Ina circuit breaker, the combination of an electromagnetic trip. device ccmprising an energizing winding, a trip member, a Sealed casing containing. a body of fluid.V and movable to engage and operate said` trip member, an armature disposed in said casing and operable upon energization of said winding in response to overload currents .below a predetermined value to move said casing, a magnetizable member having an opening therethrough disposed in said casing to be held against movement by energization of a rod disposed in said. opening cooperatingv with said. magnetizable member to define. an annular passage to control the ow of. uid past said magnetizable member to effect a time delay in the tripping movement of said casing, a second armature mounted in axial alignment with said casing and operable upon energization of said winding in response to overload currentsabove said predetermined val-ue to engage and move said casing to cause said casing to.v instantaneously operate saidtrip member, resilient means opposing tripping movement of said. casing, and means operable to vary the tension of said resilient means to vary the minimum overloadiourrent required to move. said casing.

9. In a circuit breaker, the combination of an electromagnetic. trip device comprising a fixed magnetic member and an energizing winding, a trip member, a sealed casing containing a body ofiiuid and movable within said winding to engage and actuate said trip member, a first armature disposed in said casing and having a tubular portion extending out of said casing, said armature being operable in response to overload currents below a predetermined value to move said casing, a magnetizable element having an open-- ing therethrough and disposed in said casing to be held substantially stationary during tripping movement of Said casing by energization of saidl winding in response to overload currents below said predetermined value, means biasing said magnetizable element to. one end of said casing,

a valver housing disposed in said opening and cooperating,` with said magnetizable element to define a. restricted passage for controlling displacement of iiuid. in responseto certain overload current values below said predetermined. value to eiect a relatively long time delay in the tripping movement of said casing, valve'means. in said valve housing operable in response to certain other overload current values below said predetermined. value toA increase the fluid displacement to effect a relatively short time delay in the tripping movement of said casing, and a second. armaturey disposed in` said tubular extensionoperable in .response to overload currents above said predetermined value toengage and move said: casing to cause saidi casingv to instan-Y taneously actuate. said trip member.

10. In a circuit breaker, the combination of an electromagnetic. trip ydevice comprising a xed magnetic memberand an energizing Winding, a sealed casingcontaining a' body of fluid and movable within said winding to cause a` tripping operation, a. nrst. armature disposed in said casing and having a tubularfportion. extending: out of said casing, said armature being operable in response to overload currents below a predetermined value to move said casing, a magnetizable elementhaving. an opening therethrough and disposed in said casing. to be held substantially stationary by energization of said winding in re-I sponse tor overload currents below said predetermined' value, meansnormally' biasing said magnetizable element to one end of said casing, a valve housing disposed in' said opening and cooperatingwith` said magnetizable element to define a restricted passage for controlling displacement of fluid in response to certain overload current values below said predetermined value to retard tripping movement of said casing for a relatively long time interval, valve means in said housing operable in responsev to certain other overload current values below said predetermined value to increase the fluid displacement to thereby retard tripping movement of said casing for a relatively shortv timek interval, and a second armature disposed in said'ttubular'portion and opera'- ble in response tov overload currents above said' predetermined valuejto` instantaneously move said casing.A

ll. In a. circuit breaker, an electromagnetic trip device comprising an energizing winding, a movable core structure operable upon energization of' said winding comprisingv a sealed casing disposed for tripping movementl within said Winding and containingl a body of fluid polymeric dimethyl. silicone, a first armature disposed within said ,casingV for. moving said. casing, a magnetizable member provided with. an. axially disposed opening therethrough disposed in said casing and responsive to energization of said.v winding for retarding tripping. movement of said casing, said casing and said magnetizable memberA being, disposed .for relative. movement in. response to. energization of. said. winding by overloadv currents below a predetermined Value to effect a time delay in the-tripping. movement of saidY casing, valve means disposed inY said opening in said magnetizablemember and. movable with said casing for..contro1ling. the rate of tripping movement ofV said casing, and. a second4 armature mounted externally of said casing. but in axial` alignmentv therewith and operable upon energization. of said. winding in response to overload currents above said. predetermined. value. to engage and bodily move said casing to effect an in- Number stantaneous tripping movement of said casing. 1,293,697 JEROME SANDIN. 2,357,959 HERBERT L. RAWLINS. 2,398,187 5 2,411,300 REFERENCES CITED 2,439,165 2,451,962

The following references are of record in the file of this patent:

UNITED STATES PATENTS Numbel` Name Date 1924 1,123,288 Hellmund Jan. 5, 1915 1,154,359 Basch Sept. 21, 1915 14 Name Date Canfield Feb. 11, '1919 Kouyoumjian Sept. 12, 1944 McGregor Apr. 9, 1946 Nardone Nov. 26, 1946 Graves Apr. 6, 1948 Lindstrom Oct. 19, 1948 OTHER REFERENCES Magnets, by Underhill, page 67, McGraw-Hill 10 Book C0., Inc., 370 Seventh Ave., New York, N. Y., 

